MB-7219: remove retired xdcr ns_config parameters
MB-7219: remove retired xdcr ns_config parameters

After we switch to priority checkpoint in ep_engine, the timeout
is totall controlled in hands of ep_engine and this parameter is
no longer needed.

Change-Id: Ib8ee03fa730195ec952c1d9ef3a51925ad27687d
Reviewed-on: http://review.couchbase.org/22659
Reviewed-by: Aliaksey Artamonau <3c875bcfb3adf2a65b2ae7686ca921e6c9433147@gmail.com>
Reviewed-by: Ketaki Gangal <c7141f0717da6f2e739c31892f081a1a527a34e4@gmail.com>
Tested-by: Aliaksey Kandratsenka <340b8e09ca65cd3fc686427fcfed17e87eaf61e2@gmail.com>

membase/ns_server,nimishzynga/ns_server,t3rm1n4l/ns_server,ceejatec/ns_server,vzasade/ns_server,mschoch/ns_server,ceejatec/ns_server,vzasade/ns_server,mschoch/ns_server,pavel-blagodov/ns_server,mschoch/ns_server,nimishzynga/ns_server,ceejatec/ns_server,t3rm1n4l/ns_server,pavel-blagodov/ns_server,nimishzynga/ns_server,ceejatec/ns_server,membase/ns_server,pavel-blagodov/ns_server,daverigby/ns_server,membase/ns_server,ceejatec/ns_server,nimishzynga/ns_server,vzasade/ns_server,mschoch/ns_server,membase/ns_server,daverigby/ns_server,daverigby/ns_server,pavel-blagodov/ns_server,daverigby/ns_server,nimishzynga/ns_server,nimishzynga/ns_server,t3rm1n4l/ns_server,t3rm1n4l/ns_server,ceejatec/ns_server,t3rm1n4l/ns_server,membase/ns_server,membase/ns_server,mschoch/ns_server,daverigby/ns_server,mschoch/ns_server,vzasade/ns_server